1. Field of the Invention
The present invention relates generally to monitoring security zones for intrusions and, more particularly, to a system and methods for such monitoring using, in one embodiment, a swarming, inferential sensor node network in combination with shadow/intrusion blockage detection.
2. Description of the Related Art
Various means exist today to monitor, ensure the safety of, and control access to security zones including public and private areas both large and small. Such means include video monitoring, infrared (IR) moving object detectors, and “electric eye” tripwire approaches with IR signals across key pathways.
Shortcomings with the above approaches include: 1) video monitoring is human intensive and requires many high-bandwidth camera nodes; 2) IR moving object detectors are typically placed at predictable locations and can be evaded, disabled, or countered; and 3) IR tripwire paths are specific beams along fixed paths that can be anticipated and evaded.
Distributed sensor network monitoring systems can become very complex because of the numbers of sensors needed (tens of thousands, for example) and the requirement that the sensors cooperate with each other and do so without alerting an intruder. The power requirements for such a system can become prohibitive resulting in a network of only short-term operating life. Furthermore, the complexity of the system and spectral crowding can preclude effective design.
Sensor networks have been developed (see, for example, V. K. Munirajan, “Methods for Locating Targets and Simulating Mine Detection via a Cognitive Swarm Intelligence-Based Approach,” Patent Application Pub. No. US 2006/0161405 A1, 20 Jul. 2006, and H. Van Dyke Parunak and S. Brueckner, “Decentralized Detection, Localization, and Tracking Utilizing Distribution Sensors,” Patent Application Pub. No. US 2003/0228035 A1, 11 Dec. 2003) but they have complex sensing mechanisms and algorithms.
What is needed, therefore, is a sensor network that uses simple tones with tiny, potentially expendable nodes that make scaling feasible economically as well as technically.